Judgment

The Actor sees the Victim holding a knife and rushing towards the Ward.  The Ward is an ordinary person, not known to have commited any crimes or done anything particularly bad to anyone.  The Actor knows, somehow, that the Victim honestly intend and is able to kill the Ward, and so he fires a weapon he holds at the Victim, killing him.  The Actor has no previous major engagement with either the Victim or Ward, except that which would allow him to know for sure that the Ward is innocent and the Victim intends to to the Ward harm.  There are also no other means available to the Actor to stop the Victim from harming the Ward.

Based upon this, has the Actor commited a moral act in saving the life of the Ward?  Has he commited an immoral act in killing the Victim?  Is the act of killing an aggressor a separate case from just simple killing or protecting?  For convenience, I have selected several likely possible answers:
A. The Actor, in killing the aggressor Victim to protect the innocent Ward, committed a morally good act.
B. The Actor, in killing the Victim, committed an immoral act.  However, he also commited a morally good act in saving the life of the Ward.  In this case, the act of saving a life is a greater good than the evil of killing.  Thus, he committed a necessary evil.
C. The Actor, in killing the Victim, committed an immoral act.  However, he also commited a morally good act in saving the life of the Ward.  In this case, the act of killing is a greater evil than the good of saving a live.  Thus, he committed and unjustified evil.
D. There has been no good or evil done in this situation.
E. None of these answers apply.  (Provide your own.)